Those include frequent urination, urgency of urination and sleep interruption over the need to urinate. The herb is not been shown as effective in treatment or prevention of prostate cancer, Sloan Kettering said.

A 2011 study reported by CBS Newsand published in the Journal of the American Medical Association suggested that saw palmetto is ineffective and offers no relief for prostate enlargement.

In that research, men with moderate BPH symptoms "took up to three times the standard dosage of saw palmetto - and the stuff still didn't work," CBS said.

"Now we know that even very high doses of saw palmetto make absolutely no difference," Dr. Gerald Andriole, chief of urologic surgery at Washington University School of Medicine in St. Louis, said in the statement, according to CBS.

"Men should not spend their money on this herbal supplement as a way to reduce symptoms of enlarged prostate because it clearly does not work any better than a sugar pill," he added.

Previous studies had suggested that saw palmetto seemed to counter androgens like testosterone and DHT in men, causing tissues like the prostate to take in less amounts of those hormones.

Other lab studies and those on animals have found "saw palmetto reduces the conversion of testosterone to the DHT, its more potent form, by inhibiting the enzyme 5 alpha reductase. Saw palmetto berry extracts also reduce inflammation and edema in laboratory studies by inhibiting the formation of compounds that cause these reactions," Sloan Kettering.

Saw palmetto, which is described by Everyday Health as a "palm-like plant" has berries that are used to manufacture the supplement. Typically it is sold in capsule form.

But use of it has not been approved by the Food and Drug Administration and is not a substitute for prescription drugs, the website warns. "Saw palmetto has not been evaluated by the FDA for safety, effectiveness, or purity," Everyday Health added. "All potential risks and/or advantages of saw palmetto may not be known. Additionally, there are no regulated manufacturing standards in place for these compounds."

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